A protein produced by the bioluminescent jellyfish Aequorea victoria that fluoresces in the lower green portion of the visible spectrum. The gene for green fluorescent protein (GFP) has been isolated, and the protein has been extensively characterized biochemically and found useful in biological research. After synthesis of GFP, three of its amino acids undergo a self-catalyzed reaction that produces an internal fluorophore (fluorescent molecule). The protein does not require a specific cellular environment to become fluorescent and can be artificially expressed in cell types as diverse as bacterial, plant, and animal cells. It can be attached to other proteins of interest using recombinant DNA techniques, making it possible to easily trace the synthesis, location, and movement of these proteins in single living cells using conventional fluorescence microscopy.